The present invention relates to a bias ECR (Electron Cyclotron Resonance) plasma CVD (Chemical Vapor Deposition) apparatus, and more particularly to a bias ECR plasma CVD apparatus which can reduce the number of particles being generated in a CVD reaction chamber and deposited to a film formed on a substrate (wafer).
In the recent development of ULSI (Ultra Large Scale Integration), an increase in the degree of integration and an increase in operating speed accompany increasingly severe demands to fine working techniques and cleaning techniques.
In particular, impurities and particles of foreign matter deposited on a film formed on a substrate (wafer) cause problems such as breakdown or short circuits, causing a reduction in yield and reliability. Accordingly, a reduction in the number of foreign matter particles is increasingly required in the manufacturing process for integrated circuits.
The above problem caused by the particles occurs without exception in a film forming method using a bias ECR (Electron Cyclotron Resonance) plasma CVD apparatus (which will be referred simply to as an ECR-CVD apparatus) which can flat form an insulating film or the like at low temperatures of about 200.degree.-350.degree. C.
However, a mechanism for reducing the number of particles is not generally provided in a conventional ECR-CVD apparatus.
As shown in FIG. 4, the conventional ECR-CVD apparatus is comprised of an ECR plasma generating chamber 20 and a plasma CVD chamber 21. The ECR plasma generating chamber 20 is comprised of a wave guide pipe 2 for introducing a micro (.mu.) wave (2.45 GHz) 1 into a plasma generating chamber 4 and a coil 3 surrounding the wave guide pipe 2 for applying an electromagnetic field to the microwave 1. N.sub.2 O and Ar gas 10 is supplied to the plasma generating chamber 4 and an electromagnetic field is applied to the microwave 1, thereby generating a plasma. The plasma CVD chamber 21 is comprised of a plasma reaction chamber (which will be hereinafter referred simply to as a chamber) 6 into which the plasma is fed through a plasma drawing window 5 formed of quartz to effect a plasma CVD reaction. A stock gas (e.g., SiH.sub.4) for film formation is supplied through a stock gas ring 7 into the chamber 6. In the chamber 6, the reactant gas is activated by a collision effect of ions and electrons to form a desired film on a surface of a wafer 8 as a substrate. A quartz coating 13 is formed on an inner wall of the plasma generating chamber 4 to prevent the generation of contaminants and particles such as Cr, Fe and Ni from SUS. A quartz window is provided at a micro wave introducing portion. The wafer 8 is supported on a sample bed (susceptor) 9 serving as a support bed. The ECR-CVD method applies electron cyclotron resonance, so that the power absorbing efficiency is high, and the confinement effect by a magnetic field is exhibited, thereby effecting high-density plasma generation.
In the film forming method using the conventional ECR-CVD apparatus as described above, the stock gas supplied is wholly expanded in the chamber 6, so that a reaction product is deposited on not only the surface of the wafer 8 but also an inner surface of a chamber wall 11 and exposed surfaces of the plasma drawing window 5 and the susceptor 9 (which will be hereinafter referred to as an inner surface of the chamber 6) as shown by a dashed line in FIG. 4, thus forming a film 12. It is considered that the film 12 is occasionally separated to cause the generation of the contaminant particles.
It is considered that the separation of the film 12 formed on the inner surface of the chamber 6 is caused by a difference in thermal shrinkage factors between the deposited film and the metal (e.g., SUS 308) of the inner surface of the chamber 6 due to an increase in temperature in the chamber 6 by the collision of ions and electrons existing in the plasma during the film formation and a decrease in temperature after the film formation.